The invention relates to a method for preventing an inadmissibly high speed of the load receiving means of an elevator.
Regulations for the construction and operation of elevators require means and procedures to be used, which during any phase of the elevator operation prevent an inadmissibly high speed of the load receiving means with a maximum degree of reliability.
Conventional elevators are equipped with a safety catch that, when the speed of the load receiving means reaches a defined speed limit, is activated by a speed limiting device and that brakes and stops the load receiving means with the highest admissible delay.
U.S. Pat. No. 6,170,614 B1 discloses an electronic speed limiting system that continuously receives information about the actual position of the load receiving means from a position measuring device and that calculates the actual speed from this. A microprocessor then continuously compares this actual speed with fixed-programmed limiting values applying for the entire travel way, which are assigned to certain operating modes of the elevator, for example, to an upward or downward movement. When the actual speed of the load receiving means exceeds the current active limit value, the electronic speed limiting system activates an electro-magnetically operated safety catch that stops the load receiving means.
The described electronic speed limiting system has considerable disadvantages. Every time it is detected that the limit value has been exceeded, the safety catch is activated and the operation of the elevator is thus stopped, with in most cases, passengers not being able to leave the elevator before a service engineer has returned the elevator to operation or returned the load receiving means to an access zone. Any excess speed will thus cause braking of the load receiving means with highest admissible delay values, which is extremely unpleasant for passengers and can cause anxiety and may even injure infirm persons.